c 



202 



to its parent tree, was bent so as to be placed under 

 the receiver which had been used in the last experi- 

 ment ; the water confining the common air was kept in 

 the same manner impregnated with carbonic acid gas : 

 the experiment was carried on from August 6th till 

 August 14th, 1807 ; during this time, though the 

 weather had been generally clouded, and there had 

 been some rain, the volume of elastic fluid continued to 

 increase. Its quality was examined on the morning of 

 the 15th; it contained^ of carbonic acid gas, and 

 100 parts of it afforded 23.5 of oxygene gas. 



These facts confirm the popular opinion, that 

 when the leaves of vegetables perform their healthy 

 functions, they tend to purify the atmosphere in the 

 common variations of weather, and changes from light 

 to darkness. 



In germination, and at the time of the decay of 

 the leaf, oxygene must be absorbed ; but when it is 

 considered how large a part of the surface of the 

 earth is clothed with perennial grasses, and that half 

 of the globe is always exposed to the solar light, it ap- 

 pears by far the most probable opinion, that more 

 oxygene is produced than consumed during the pro- 

 cess of vegetation ; and that it is this circumstance 

 which is the principal cause of the uniformity of the 

 constitution of the atmosphere. 



Animals produce no oxygene gas during the ex- 

 ercise of any of their functions and they are constantly 

 consuming it ; but the extent of the animal, compar- 

 ed to that of the vegetable, kingdom is very small ; 

 and the quantity of carbonic acid gas produced 



